Recently, there has been considerable interest within the detergent industry for laundry detergents which are "compact" and therefore, have low dosage volumes. To facilitate production of these so-called low dosage detergents, many attempts have been made to produce high bulk density detergents, for example with a density of 600 g/l or higher. The low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers, especially in households where there is a premium on storage space.
Generally, there are two primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules. In the second type of process, the various detergent components are dry mixed just prior to agglomeration with a binder, such as a nonionic surfactant. In the latter process in which the starting detergent materials are mixed together prior to agglomeration, there has been difficulty in producing consistent, free flowing, detergent agglomerates having the desired high density, especially when there is a high amount of binder present e.g. about 10% or higher.
The art is replete with disclosures of detergent compositions containing anhydrous materials such as carbonates and sulfates. For example, Kaminsky (commonly assigned), U.S. Pat. No. 4,487,710, discloses a granular detergent composition containing an anionic surfactant, an anhydrous material such as carbonates and sulfates, and an ethoxylated surfactant solubility aid. While the detergent composition is produced by agglomeration, it is not produced from a viscous surfactant paste, typically having a high water content e.g. 10% or higher. In the past, there has been difficulty in producing free flowing detergent agglomerates from such a surfactant paste which has been agglomerated.
Further, there has also been difficulty in attaining high levels of surfactant in the resulting detergent agglomerates, a feature which facilitates production of low dosage detergents. More particularly, any increase in the density of granules produced by way of conventional spray drying techniques is limited by the relative amount of surfactant required to be passed through the spray drying tower. By providing a detergent agglomerate admix having a high surfactant level, the amount of surfactant passed through the spray drying tower can be reduced, thereby increasing the density of the exiting granules and ultimately the finished detergent. Thus, it would be desirable to have a process by which detergent agglomerates having higher surfactant levels can be produced.
The art is also replete with disclosures of agglomerating detergent compositions, some of which contain anhydrous materials. For example, Curtis, European patent application No. 451,894 (Unilever), discloses a process for preparing high density detergent granules by using two mixers in series. In particular, an admix of starting detergent materials are fed into a high speed mixer/densifier after which the materials are fed into a moderate speed mixer/densifier to increase the bulk density further. Thus, Curtis initially requires a high speed mixer/densifier to pulverize the detergent granules and then a second moderate speed mixer/densifier to increase the density to the desired level. Again, the Curtis process does not entail agglomerating a viscous surfactant paste.
Accordingly, despite the above-described disclosures in the art, it would be desirable to have a process for producing high density detergent agglomerates having a density of at least 650 g/l from a viscous surfactant paste among other starting detergent components. It would also be desirable for such a process to produce detergent agglomerates having higher levels of surfactant to aid in the production of low dosage detergents and admixes therefor.